Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$82.76	11.370%	$92.1698	$92.17	$92.15	$92.20
Purchase #2	$172.94	13.322%	$195.9791	$195.98	$196.00	$196.00
Purchase #3	$109.68	11.105%	$121.86	$121.86	$121.85	$121.90
Purchase #4	$106.76	4.409%	$111.467	$111.47	$111.45	$111.50
Purchase #5	$51.38	3.794%	$53.3294	$53.33	$53.35	$53.30
Purchase #6	$159.35	9.476%	$174.45	$174.45	$174.45	$174.50
Purchase #7	$98.80	8.493%	$107.1911	$107.19	$107.20	$107.20
7 purchase totals =	$781.67		$856.4464	$856.45	$856.45	$856.60